This project will investigate in the medulla of cat single cell firing patterns by microelectrode recording which are related to respiration. Both afferent pathways from periphery and efferent pathways to spinal cord will be investigated. The particular targets will be nucleus solitarius and nucleus retroambigualis. Work already in progress has already identified by microelectrode stimulation and antidromic invasion many of the respiratory cells which project axons into spinal cord and has defined the pathways over which the axons run. This work will be continued particularly to identify those regions of n. solitarius which project to cord. Three general classes of cells have been identified (1) those whose firing is locked to cranial nerve afferent input (2) a group similar to the first but which generate a respiratory rhythm in the absence of peripheral input (3) a group projecting to cord whose firing closely matches respiratory movement but is only very indirectly coupled to the afferents. The aim of the project is for these three groups of cells which contain inspiratory and expiratory subgroups A) to locate the cells and the course of their axon projection; B) to study the relationship of their firing to each other within a group and between groups; C) to study the pathway of afferent projection onto them. The general aim is to discover the mechanism by which medulla cells organise and generate orders to form the respiratory movement pattern.